The present invention relates to frictionless hydraulic dampers and to frictionless hydraulic dampers which can also function as snubbers, and, more specifically, the present specification is directed to alternate embodiments of the subject matter disclosed in U.S. patent application Ser. No. 752,094, filed July 5, 1985, now U.S. Pat. No. 4,638,895, dated Jan. 27, 1987.
By way of background, frictionless hydraulic dampers are desired for certain applications to attenuate forces between relatively movable objects where the internal frictional resistance of the dampers is objectionable. There are certain hydraulic devices which function solely as dampers, and there are other hydraulic devices which function as dampers when they are subjected to forces at low velocities and also function as snubbers when they are subjected to forces at high velocities. By way of definition, a hydraulic snubber must always function as a damper when placed between relatively moving external members which move relative to each other below a predetermined velocity, and it functions as a snubber when the external members move relative to each other above the predetermined velocity.
By way of further background, and by way of specific example, in power plants and in other installations small pipes are suspended by hangers in the nature of snubbers which are subjected to forces within the 200 to 3,000 pound range. In the past it has been highly impractical to use hydraulic snubbers for this application for the following reason. The seals create friction, and where small pipes were suspended by snubbers which were subjected to forces between 200 and 500 pounds, the seal friction was a substantial portion of the applied forces which did not allow the small pipe to move in an unrestrained manner while being supported. Therefore, in the past hydraulic snubbers were not used for the foregoing application, and instead highly complex mechanical snubbers were used. These required high maintenance and many times were unreliable because of their complexity.